Merlin Heads

CastleMGBV8 · Post by **CastleMGBV8** » Wed Jun 16, 2010 7:35 pm

Mark,

Apologies, I was forgetting that the heads came fully assembled and if the springs were already shimmed to achieve the correct installed height then they should be correct for the job.

As you have had problems it would suggest all is not as it should be and possibly either the installed height is not correct or you have got a set of soft springs.

Keep kicking RS's backside until you get some sensible answers.

Kevin.

minorv8 · Post by **minorv8** » Thu Jun 17, 2010 7:01 am

I don´t know either which springs are fitted to the heads. I have assumed that they are the single ones advertised in their catalogue. I am not sure how high I have revved the engine but have not had similar problems. I did have a problem with a pushrod. I do get serious bleed down with lifters overnight and one morning there was loud ticking. It disappeared a few seconds after I started the engine but the engine ran only with 7 cylinders. I removed the cover and found one pushrod loose, wedged between the block and head. No damage, just put it back into place. I am running thicker Compcams pushrods and it is possible that it runs quite close to the head ? During dry build there is adequate clearance but since I dont run spacers in the rocker assembly the rockers may move sideways and let the pushrod just touch the head casting.

mgbloke · Post by **mgbloke** » Thu Jun 17, 2010 11:05 am

Just had a reply from RS they are sending me some new springs
Result!

JP. · Post by **JP.** » Thu Jun 17, 2010 2:01 pm

Please let us know if they arrive which ones they are.
Ill guess there will be a Real Steel partnumber on the bag.
Could be handy for us Merlin heads users in the future.

Thanks in advance

mgbloke · Post by **mgbloke** » Thu Jun 17, 2010 6:06 pm

JP
Tell us about your merlin heads, what performance you got?

Mark

mgbloke · Post by **mgbloke** » Thu Jun 17, 2010 6:19 pm

Springs were dispached today.
Is there an easy way to change the springs without removing heads.
Ive heard of people feeding rope in through the spark plug holes to keep the valves up. What about compressing the spring?
Apparently the installed height will be the same.

Mark

unstable load · Post by **unstable load** » Thu Jun 17, 2010 6:55 pm

The rope trick is an aircraft industry thing. Our cylinders are head and sleeve as a unit part so a spring job becomes a cylinder off nightmare and the rope is a way of keeping the valve from falling into the pot while the spring compressor does it's magic.
You could also use compressed air to achieve a similar result.

JP. · Post by **JP.** » Thu Jun 17, 2010 7:05 pm

Not shure about the horsepower gain.......
Meaning yess had gain but as I switched rolling road at that time it not very accurate.
What I had on the engine with standard heads with Rolling Road number 1
I now had on the wheels with the Merlin heads fitted but that was measured at Rolling road number 2
So guess its about 30-35bhp gain.
It gave me instand 1.7 sec on the ¼mile for shure with more to come.

Had some personal issues with the guys from Rolling road number 1 so I switched to number 2.
As no roller will give the same readouts like the other (meaning you can visit four differend Dyno's on a day with differend readouts afterall in accurate bhp) I can not suplie the real gain.

For spring change............its like changing stemseals with airpressure.
Just hook up the compressor to the sparkplug hole with the piston on TDC @ fire and transmission in 1th gear.
I modifiet an old sparkplug and welded an airnipple to it

I don't think the rope maner will work with the small 14mm sparkplug holes which the merlin heads have.

With the piston at TDC @ fire if something happens the valve can not fall into the cilinder. @ fire are both valves closed.

mgbloke · Post by **mgbloke** » Fri Jun 18, 2010 6:08 pm

JP
I understand what you are saying about different rolling road readings but if I had gained the difference between Rwhp and flywheel hp it would be 50bhp.
Im thinking of taking mine to another rolling road to see how it compares.

Have decided to remove heads to do the valve springs.

Mark

minorv8 · Post by **minorv8** » Sat Jun 19, 2010 7:05 am

Being a lazy bas***d I would make a tool for compressing the valves in situ. I have done the swap earlier but with a tool borrowed from a friend. You could use a rocker shaft and pillars for support and make a L shaped lever, something along the link below.

http://www.speedwaymotors.com/VALVE-SPR ... R,601.html

Here is another option:

http://www.mytoolstore.com/kd/kdengi13.html (last on the page)

mgbloke · Post by **mgbloke** » Sat Jun 19, 2010 7:46 am

Jukka
I might have a go at making a tool, would save a lot of effort and cost of new gaskets.

I received the new springs today. They are made by Comp Cams
Numbers on box 981-16. seat load 105lbs@1.700". open :273lbs@1.25 spring rate 370lbs/in coil bind 1.150
They measure 2" long and have an inner flat coil which isnt as long as the outer spring, presumably to keep the coils in line when they compress?

Would be good If I can get them fitted by my next event 25th June.

Mark

minorv8 · Post by **minorv8** » Sat Jun 19, 2010 8:29 am

Comp Cams Beehive version is 26981. They require new retainers, 787-16.

Flat spring inside is often described as damper.

CastleMGBV8 · Post by **CastleMGBV8** » Sat Jun 19, 2010 8:49 am

Mark,

One of these would appear to do the job.

http://www.tooled-up.com/Product.asp?PID=28929

Kevin.

bigaldart · Post by **bigaldart** » Sat Jun 19, 2010 3:38 pm

JP,

What car do you run and what does it weigh, 1.7 in the quarter sounds like a lot more than 35 bhp to me. 70 bhp would gain us about .5 in ET, but we only weigh 1600 lbs.

Alan

mgbloke · Post by **mgbloke** » Thu Jun 24, 2010 1:28 pm

Well it was a bit of a slog but Valve springs now changed. Im glad I decided to remove heads as they were a real sod. The retainers seem to stick, Had to beef up my valve spring compressor to do it.
While it was apart I measured for the rocker shaft end supports and will have some new ones made that fit.
My only worry is that the head gaskets were a bit cheap compared to the ones I took off.
Anyway looking forward to my trackday tomorrow.

Mark